New solid state refrigeration techniques are based mainly on two principles: adiabatic demagnetization cooling or adiabatic depolarization cooling. The last one is called electrocaloric refrigeration and it employs the electrocaloric effect (ECE) which consist in the change in temperature of a material upon the application or removal of an electric field, under adiabatic conditions. Ferroelectrics and relaxors are regarded as promising candidates that can easily find out their giant ECE because of their large polarization and their field and temperature-induced structural transitions, however they are usually Pb-based materials which should be replaced with environmentally friendly equivalent oxides.

Among the ferroelectric Pb-free systems, BaTiO₃ family has been studied quite extensively for EC applications, but at fundamental level some problems were never elucidated like for example, if there is an optimal size and composition in BaM_xTi_1-xO₃ systems for which the ECE can be maximized. Our idea is to explore the possibility of enhancing the ECE by using critical conditions, i.e. compositional or temperature-induced structural phase transitions, morphotropic phase boundaries or critical scale effect, if present. The aim of the present project is to develop a complex modelling-experimental approach to understand the role of composition and grain size under critical conditions in enhancing electrocaloric properties of BaTiO₃-based lead-free ferroelectric ceramics. For this aim, BaM_xTi_1-xO₃ (M⁴⁺=Sn/Zr/Ce/Hf) dense ceramics, with compositions near the tri-critical point and variable grain sizes will be comparatively investigated and their EC properties will be explored and described by appropriate models. The project will develop original models for describing size dependent properties in BaTiO3-based solid solutions with phase superposition and will develop for the first time in Romania a methodology for measuring and evaluating the ECE in ferroelectric ceramics.

Project budget

Project manager: lect.dr.habil. Lavinia-Petronela Curecheriu
Prof.univ.dr. Liliana Mitoseriu
Lect.dr. Leontin Padurariu
PhD Student: Vlad-Alexandru Lukacs
Master Student: Teodora Sandu

Stage I – 2020
Understanding the role of the phase superposition on the electrocaloric properties in Ba-based lead free ceramics:

1.1 Synthesis and micro/nano structural characterization of BaMxTi1-xO3 powders with different size & shapes by innovative processing including combined methods
1.2 Development of models for describing the phase superposition in BaTiO3-based solid solutions (to be continue in 2021)
1.3 Dissemination, coordination, management

Stage II – 2021
Understanding the role of the phase superposition and grain size on the electrocaloric properties in Ba-based lead free ceramics:

2.1 Preparation & structural characterisation of BaMxTi1-xO3 ceramics with composition around phase superposition: monitoring the effect of composition on the structural modifications;
2.2 Raman investigation of the role of composition and temperature on the local structure of BaMxTi1-xO3 ceramics;
2.3 Low-field broadband dielectric spectroscopy of BaMxTi1-xO3 ceramics;
2.4 Investigation of compositional effect on high field properties from mesoscale (AFM/PFM) to macroscale (P(E), tunability);
2.5 Investigation of phase superposition induced by composition on the electrocaloric properties;
2.6 Development of models for describing the phase superposition in BaTiO3-based solid solutions(finish)
2.7 Mesoscale models (Landau theory with FEM calculations) for describing the composition effect on the electrocaloric properties in BaMxTi1-xO3 ceramics
2.8 Preparation of BaMxTi1-xO3 ceramics with different grain sizes by solid state methods (to be continue in 2022)
2.9 Structural & microstructural characterisation of BaMxTi1-xO3 (to be continue in 2022)
2.10 Development of a model for describing size effects on the low- field properties in BaTiO3-based ceramics (to be continue in 2022)
2.11 Dissemination, coordination, management

Stage III – 2022
Exploring scale-dependent electrocaloric properties in BT-based lead-free ceramics in the range of phase superposition

3.1 Preparation of BaMxTi1-xO3 ceramics with different grain sizes by solid state methods (finish)
3.2 Structural & microstructural characterisation of BaMxTi1-xO3 (finish)
3.3 Study of the temperature-dependent low-field dielectric properties by impedance spectroscopy;
3.4 Macroscopic ferroelectric (P(E), sub-switching experiments) and dc-tunability study
3.5 II.1.5 Investigation of the role of GS on the electrocaloric effect in BaMxTi1-xO3 ceramics
3.6 Development of a model for describing size effects on the low- field properties in BaTiO3-based ceramics (finish)
3.7 Mesoscale modelling (Landau-based theory with FEM calculations) to describe size effects on the electrocaloric properties in BaMxTi1-xO3 ceramics with phase superposition.
3.8 Dissemination, coordination, management

Raportare Stiintifica 2020

Raportare Stiintifica 2021

Raportare Stiintifica 2022

Raport sintetic Final

Results (English)

ISI Papers

[L1] - Lavinia Curecheriu, Teodora Sandu, Oana Condurache, Giovanna Canu, Chiara Costa, Maria Teresa Buscaglia,  Mihai Asandulesa,  Juras Banys, Vincenzo Buscaglia and Liliana Mitoseriu, Dielectric, ferroelectric and electrocaloric properties of 1%Eu-doped BaZr_yTi_1-yO₃ ceramics, Materials Research Bulletin 157, 112034 (2023)

[L2] Lavinia Curecheriu, Maria Teresa Buscaglia,  Vlad-Alexandru Lukacs, Leontin Padurariu, Cristina Ciomaga, Role of density and grain size on the electrocaloric effect in Ba_0.90Ca_0.10TiO₃ ceramics, Materials 15, 7825 (2022)

[L3] Cristina E. Ciomaga, Lavinia P. Curecheriu, Vlad A. Lukacs, Nadejda Horchidan, Florica Doroftei, Renaud Valois, Megane Lheureux, Marie Helene Chambrier, Liliana Mitoseriu, Optimization of processing steps for superior functional properties of (Ba,Ca)(Zr,Ti)O₃ ceramics, Materials (accepted)

[L4] Leontin Padurariu, Nadejda Horchidan, Lavinia Curecheriu, Liliana Mitoseriu, Enhancing the pyroelectric effect in BaTiO₃- based ceramics by tailoring phase composition, Applied Physics Letters (manuscript in preparation)

[L5] - Teodora Sandu, Lavinia Curecheriu, Leontin Padurariu, Cristina Ciomaga, Vlad-Alexandru Lukacs, Liliana Mitoseriu, Role of composition on the electrocaloric properties of BaM_xTi_1-xO₃ ceramics (manuscript in preparation)

Participation to international conferences

[C1]  L. Curecheriu, Size-dependet properties in BaTiO₃-based ceramics, International Conference on Minerals, Metallurgy and Materials, 22-23 Martie 2021, online -keynote

[C2] L. Curecheriu, V-Al. Lukacs, L. Pădurariu, C. Ciomaga, L. Mitoseriu, Electrocaloric effect in BaZr_xTi_1-xO₃ ceramics, International Conference Processes in Isotopes and Molecules, PIM 2021 (oral)

[C3] L. Curecheriu, V-Al. Lukacs, T. Matei, L. Pădurariu, C. Ciomaga, L. Mitoseriu, Role of critical parameters (composition and phase superposition) on the electrocaloric properties of BaZr_xTi_1-xO₃ ceramics, 11th International Advances in Applied Physics& Materials Science Congress & Exhibition, 17- 23 Octombrie 2021 -invited

[C4] L. Curecheriu, V-Al. Lukacs, T. Matei, L. Pădurariu, L. Mitoseriu, Role of composition on the electrocaloric properties of BaM_xTi_1-xO₃ ceramics, Sixth International Symposium on Dielectric Materials and Applications, 15-17 Decembrie 2021 – oral

[C5] Lavinia Curecheriu, Maria Teresa Buscaglia, Giovanna Canu, Cristina Ciomaga, Leontin Padurariu, Vincenzo Buscaglia, Liliana Mitoseriu, Size-dependent properties in BaTiO₃- based ceramics, Webinar on Science, Engineering and Technology, 26-28 ianuarie 2022 (oral)

[C6] Lavinia Curecheriu, Teodora Sandu, Vlad Al. Lukacs, Leontin Padurariu, Cristina Ciomaga, Liliana Mitoseriu, Exploring critical conditions (composition and grain size) as a new tool for enhancing electrocaloric properties of BaTiO₃ – based ceramics, Ceramics in Europe, 10-14 iulie 2022, Cracovia, Polonia (oral)

[C7] Teodora Sandu, Vlad Al. Lukacs, Lavinia Curecheriu, Liliana Mitoseriu, Investigation of the electrical properties of hafnium doped barium-titanate ceramics, Ceramics in Europe, 10-14 iulie 2022, Cracovia, Polonia (oral)

[C7] Lavinia Curecheriu, Electrocaloric effect in lead-free ferroelectric ceramics,  International Workshop on Advanced Materials and Applications, 28-29 octombrie 2022, online

Dissertation thesis

Teodora Sandu, BaTiO₃-based ferroelectric ceramics for energy storage and harvesting, Physics for Advanced Technologies, Faculty of Physics, Alexandru Ioan Cuza University

Workshop

International Workshop on Advanced Materials and Applications, 28-29 octombrie 2022, online